1. Field of the Invention
The present invention relates to moulding compositions of polycarbonates and graft polymers and optionally further additives and components, which have, in addition to a high resistance to chemicals, a good resistance to heat, in particular a low tendency towards yellowing and a low tendency towards degradation when exposed to heat.
2. Description of Related Art
In a particular, flameproofed embodiment, the after-burn time in a UL94 classification is furthermore reduced.
Thermoplastic moulding compositions of polycarbonates and ABS polymers have been known for a long time.
DE-A 1 170 141 describes readily processable moulding compositions of polycarbonates and graft polymers of monomer mixtures of acrylonitrile and an aromatic vinyl-hydrocarbon on polybutadiene.
DE-A 1 810 993 describes the improved heat resistance of polycarbonate in a blend with ABS graft polymers or copolymers based on α-methylstyrene.
The subject matter of DE-A 22 59 565 and DE-A 23 29 548 is the improved flow line strength of PC/ABS moulding compositions, graft polymers of a certain particle size being in each case used as a constituent of the ABS component in both documents.
DE-A 28 18 679 describes PC/ABS mixtures having a particularly high toughness at low temperatures if the ABS polymer comprises two graft copolymers of different degree of grafting.
EP-A 900 827 discloses impact-modified polycarbonate compositions with improved heat stability comprising emulsion polymers which are substantially free from any basic components which degrade the polycarbonate. According to this application, such polycarbonate compositions which are impact-modified with emulsion polymers, which contain basic impurities due to the preparation, have a lack of heat stability.
EP 0 363 608 describes polymer mixtures of aromatic polycarbonate, styrene-containing copolymer or graft copolymer and oligomeric phosphates as flameproofing additives.
EP 0 704 488 describes moulding compositions of aromatic polycarbonate, styrene-containing copolymers and graft polymers having a specific graft base in certain ratios of amounts. These moulding compositions can optionally be rendered flame-resistant with phosphorus compounds.
EP 747 424 describes thermoplastic resins which comprise phosphate compounds having a molecular weight of from 500 to 2,000 and phosphate compounds having a molecular weight of from 2,300 to 11,000 as flameproofing agents, a large number of thermoplastic resins being listed. The flow properties of the moulding compositions are impaired significantly by the high molecular weights of the phosphorus compounds.
EP 1 003 809 describes PC/ABS moulding compositions which comprise oligomeric phosphorus compounds and graft polymers of a graft base having a certain particle size. These moulding compositions are distinguished by good mechanical properties, in particular also under increased elasticity stress.
EP 0 983 315 describes moulding compositions of aromatic polycarbonate, graft polymer and a flameproofing agent combination of a monomeric and an oligomeric phosphorus compound. These moulding compositions have a high heat distortion point and excellent mechanical properties (notched impact strength and weld strength).
In none of the abovementioned documents is the influence of the content of free, i.e. not chemically bonded, bisphenol A on the heat stability or the tendency towards yellowing of the polycarbonate moulding compositions described, just as little as the combination of these properties with an improved resistance to chemicals is described.